Patent GB-780190-A (GB)
Title: Improvements in or relating to vehicle control systems
Inventor: MARTIN RONALD GEORGE JOHN
IPC: B61L3/12
Filed: 1954-02-17
Abstract: 780,190. Actuating signals on trains and stopping trains. PLESSEY CO., Ltd. Feb. 16, 1955 [Feb. 17, 1954], No. 4618/54. Class 105. [Also in Group XXXIX] In train control and cab signalling apparatus employing permanent and electromagnets on the track to influence an inductive element on a vehicle passing thereover to effect control of the vehicle, the cab apparatus comprises a plurality of transductors which are operated in series from pulses generated by an inductive coil or transductor passing over the magnet system to control the energization of a solenoid such as one which controls an electro-pneumatic valve controlling the vehicle braking system and/or the energization of a solenoid controlling the vehicle traction power supply and/or audible and/or visual signal on the vehicle. Such solenoid may be adapted to disconnect the power supply as used on electric and dieselelectric trains or to operate the fuel injector on a diesel engine to reduce the power output in addition to or alternatively to operating the braking system. The magnet system may have the permanent and electromagnets in axial alignment parallel to the track and with like poles adjacent each other or the magnets may be disposed with their axes vertical side by side with opposite poles uppermost. The flip-flop transductors B, H, J, L are auto-selfexcited bridge rectifying transductors which by the addition of positive feedback are made inherently unstable and so have two discrete stable operating conditions. The bias windings X of the flip-flop B gives the minimum current condition and the reset winding W on operation of the reset key N, enables restoration of the flip-flop B so maximum current condition. Flip-flops Hand L are oscillators by virtue of the positive feedback windings being connected in series with timing capacitors and bias windings Y and Z ensure cessation of the oscillators at the end of the cycle following cessation of the input'signal. Flip-flop B is normally in the maximum current condition so is unaffected by the first pulse arranged to be positive, generated in the inductive coil A as it passes firstly over the permanent magnet of the magnet system, the second pulse being negative drives the flipflop B to minimum current condition and the B output is applied to a delay capacitor D acting as a slug to the solenoid E which holds the brake-valve in the " brakes-off position, e.g. for three seconds. The drop in the B output operates the polarized indicator F. Should the signal associated with the magnet system be at " stop " and the electromagnet de-energized, no further pulse is generated in the coil A and at the end of the delay period the current ceases to flow through the solenoid E and the brakes are applied, air passing into the train braking system passing through a horn giving an audible signal. Should the signal be at " clear," a third pulse of the same sign as the second pulse is generated in the coil A and has no effect and the fourth pulse of opposite sign, or positive, returns the flip-flop B to its maximum current condition before the expiry of the delay period so that the solenoid E remains energized and the brakes are held, but the indicator F remains operated. The positive B output derived from the capacitor D operates into a bell timing flip-flop H which rises to maximum current condition and remains so for a period determined by the timing resistance R5 and capacity C2. The H output is applied to the flip-flop oscillator L to allow it to function for the determined period to operate the bell M. The flip-flop J operates only when the current through the solenoid E ceases and the brakes are applied and prevents the bell M from ringing when the vehicle passes two or more successive " stop " signals should the driver omit to press the reset key N. This key N disconnects the trip coil of the indicator F to reset the indicator in addition to resetting the flip-flop B. The pulses are fed from the coil A to the flip-flop B through a network of resistances R1, R2, R3, R4 so that if coil A is disconnected the flip-flop B receives a pulse designed to drive it to minimum current condition to effect braking of the vehicle. A flipflop transductor may be inserted to control the inductor F and a saturable reactor controlled from the flip-flop B may feed the flip-flop H and the flip-flop controlling the indicator F, the flip-flop H feeding into a bell saturable reactor which controls the flip-flop L.